Thread protector



Sept. 19, 1961 M. M. BOWMAN, JR

THREAD PROTECTOR 2 Sheets-Sheet 1 Filed Feb. 12, 1958 INVENTOR.

MARK M.BOWMAN JR. BY/I/WQQQ/W A TTO/PNEVS Sept. 19, 1961 M. M. BOWMAN, JR

THREAD PROTECTOR 2 Sheets-Sheet 2 Filed Feb. 12, 1958 42 A 0 n b/ FIG. .5

FIG. 4

INVENTOR. MARK M. BOWMAN JR BY HM W M A TTO/PNEYS niiCd States Patent- 9 ware Filed Feb. 12, 1958, Ser. No. 714,810 7 Claims. (Cl. 138-96) This invention relates to thread protectors and more particularly to thread protectors used on threaded articles to cover and protect threads during handling and storage of the threaded article. In one of its aspects the invention relates to a novel thread protector which combines the rigidity of metal with the flexiblity of a rigid plastic material such as solid polyethylene to produce an improved thread protector.

A principal object of the invention is to provide a thread protector which' will absorb impact blows. Another object of the invention isto provide athread protector which can be fabricated easilyand economically. It is also an object of the invention to provide a thread protector which combines resistance to high impact loads with resistance to cutting by contact with sharp objects. The provision of a thread protector which is both easily and rapidly removed from the threads at the site of use with no danger to workmen of splinters or bruises is still another object of the invention. Other and further objects and advantages of the invention will be apparent to one skilled in the art upon reading the detailed description of the invention and the appended drawing.

FIGURE 1 of the drawing is a view of an externally threaded pipe end partially in axial cross-section and partially in perspective with a preferred embodiment of the thread protector of the invention applied thereto;

FIGURE 2 is a view of a modification of the thread protector of FIGURE 1;

ICE

2 '1'? prises steel shell 23 and plastic body 24 having threads -25 adapted to coactwith the pipe threads 21 so as to secure the thread protector in place with the end of the pipe 22 in contact with shoulder 26. Ribs 27 of ,body 24 provide a close fit with body 24 and shell 23. Shell 23 is crimped over plastic body 24 as shown at 28. 1 In FIGURE 3 thread protector 30 is shown applied to the threaded end 31 of pipe 32. Thread protector 30 comprises metal shell 33 and plastic body 34 having threads 35 adapted to coact with threads 31 on the pipe to secure the thread protector 30 to the end of pipe 32 with the end of the pipe in contact with shoulder 36. The metal shell 33 is crimped over the plastic body as shown at 37. The plastic body has a plurality of lateral perforations indicated at 38.

' FIGURE 4 shows an embodiment of the thread protector of this invention wherein the thread protector 40 FIGURE 3 is a view of a modification of the thread protector of FIGURE 1; I

FIGURE 4 is an axial sectional view of a pipeend having a'thread protector applied thereto which comprises another embodiment of the present invention; and

FIGURE 5 shows a modification of the thread protector of FIGURE 4.

I have provided a thread protector which combines the elasticity and plasticity of solid polyethylene with the rigidity of metal, such as steel, and utilizes these features in combination to provide an improved thread protector. My improved thread protector is made by encasing a cylinder of a pliable material such as rigid polyethylene in a thin metal cup. The pliable material is threaded to mate with the thread on a pipe or other object where the threads are to be protected. I have also provided a thread protector comprising a cup of double wall construction with a resilient filler between the walls. The resilient member between the .two walls of the thread protector absorbs impact loads so as to protect the threads. The resilient means between the walls of the thread protector can be of metal or can be of plastic materials such as rigid polyethylene. Referring now to the drawing and particularly to FIGURE 1, thread protector 10 is shown applied to the threaded end 11 of pipe 12. The thread protector comprises metal shell 13 containing the plastic body 14 having longitudinal perforations 15 therethrough. Threads 16'of the plastic body 14 coact with threads 11 of the pipe to secure the thread'protector in place so as to butt the end of the pipe'against the shoulder 17. The metal shell 13 of the thread protector is crimped over the plastic body .as shown at '18.

FIGURE 2 shows thread protector 20 applied to the threaded end 21 of pipe 22. Thread protector 20 comis applied to the threaded end 41 of pipe 42. Thread protector 40 is composed of cylinder 43 having internal threads 44 and cylinder 45 having crimped edge 46. Corrugated sleeve 47 is positioned in the annulus between the cylindrical members 43 and 45 and is confined in the annulus by the end plates 48. An annular space 50 in end plate 48 allows cylinder 45 and sleeve 47 to absorb impact blows. Cylinder members 43 and 45 can be welded together at the junction of the cylinders. .1 FIGURE 5 shows a modification of the thread protector of FIGURE 4 wherein the corrugated sleeve 47 of FIGURE -4 is replaced by a coil of a resilient tubing material indicated at 49.

In the embodiment of the invention shown in FIG- URES 4 and 5 the cylindrical members are preferably made of thin gage metal, such as steel, but can be made of a non-metal such as rigid polyethylene.

The corrugated sleeve of FIGURE 4 can be made of metal or rigid polyethylene or any substantially rigid material capable of absorbing an impact blow. Similarly the spiral or coil of tubing of FIGURE 5 can be of solid polyethylene or a soft metal such as copper, aluminum, lead, etc.

The energy absorbing material of the embodiment of FIGURES 1, 2 and 3 can be a pliable material such as rigid plastic materials, rubber, etc. which is sufiiciently rigid for formation of threads therein and which has sufi'icient pliability to absorb impact blows encountered in the normal handling of the threaded article.

Rigid plastic materials are generally preferred over rubber for the reason that rubber normally does not possess suificient rigidity to absorb severe impact blows and normally does not have sufllcient rigidity to form satisfactory threads., Rigid plastic materials which are applicable for use in the present invention include polyethylene, polyvinylchloride, polytetrafiuoroethylene, and the like. Particularly applicable for use in the present invention is a polymer of ethylene or other l-olefin prepared according to patent application Serial No. 573,877, filedMarch 26, 1956,,by I. P. Hogan, et al., now US. Patent 2,825,721, issued March 4, 1958. As set forth in that application in more detail unique polymers and copolymers can be produced by contacting one or more olefins with a catalyst comprising, as an essential in gredient, chromium oxide, preferably including a sub.- stantial amount of hexavalent chromium. The chromium oxide is ordinarily associated with at least one other oxide, particularly at least one oxide selected from the group consisting of silica, alumina, zirconia, and thoria. One satisfactory method for producing the catalyst comprises the use of a steam-aged commercial cracking catalyst comprising a coprecipitated gel containing approximately weight percent silica and 10 weight percent alumina. Such gel is impregnated with an aqueous solution of a chromium compound ignitable to chromium oxide. Examples of suchcompounds are chromium trioxide, chromium nitrate, chromium acetate, and am"- moniachromate. The composite resulting from the impregnation step is dried and then contacted for a period of several hours at a temperature of about 450 to about 1500 F., preferably from about 900 to about 1000" F., i

for example, with a stream of substantially anhydrous oxygen-containing gas, such as air. The olefin feed used for polymerization is at least one olefin selected from the class of l-olefins having maximum chain length of 8 carbon atoms and no branching nearer the double hand than the 4-position. Examples of such olefins are ethylene, propene, l-butene, and l-pentene. Copolymers, such as 'ethylene-propene copolymers, can be prepared by the described method. The polymerization can be ef- 7 fected at a temperature in the range of 15 to 450 F. The pressure can range from approximately atmospheric to as high as 1000 psi.

A satisfactory method of conducting the polymerization comprises contacting an olefin with a slurry of a catalyst in a hydrocarbon sol-vent which can exist as a liquid at the temperature of polymerization. In such a case, reaction pressure need to be only sufficient to maintain the solvent substantially in the liquid phase and will ordinarily range from about 100 to 700 p.s.i.

Suitable solvents for use in the above-described process are hydrocarbons which are liquid and chemically inert under the reaction conditions. Solvents which can be used advantageously include paraffins, such as those having 3 to 12 and preferably 5 to 9 carbon atoms per molecule, for example, 2,4-trimethylpentene (isooctane), normal hexene, normal decane, isopentane, and the like. Another class of solvents which can be used are napthenic hydrocarbons having from 5 to 6 carbon atoms in the .naphthene ring, and which can be maintained in the liquid phase under the polymerization conditions. Examples of such naphthenic hydrocarbons are cyclohexane, cyclopentene, methylcyclopentene, methylcyclohexane, ethylcyclohexane, the methylethylcyclopentenes, the

4 ing a plurality of ridges of polyethylene separated by void spaces and, FIGURE 3 shows a plurality of radial perforations in the polyethylene cylinder.

A satisfactory ratio of void space to rigid polyethylene is from about 30 percent to about 60 percent void space. The void space in the modifications, shown in FIGURES 1 and 3, will preferably be about 30 percent whereas the void space in the modification of FIGURE '2 can be from 50 to 60 percent.

The polyethylene cylinder should have an overall wall thickness of from A: to about of an inch. For most applications the wall thickness will properly be in the range of about A to about /2 inch because this amount of polyethylene will provide adequate protection without adding undue bulk to the thread protector. In this respect, polyethylene is superior to rubber because a greater mass of rubber will be required to provide the same impact absorbing characteristics as the required amount of polyethylene. The thread protector provides a smooth, flush fit with the inside of the pipe'ends so that water is not retained in the pipe which often is stacked out of 'doors with the result that opportunity of corrosion of the threads is reduced.

Reasonable variations and modifications are possible within the scope of this disclosure without departing from the spirit and scope of the invention.

That which is claimed is:

1. A thread protector comprising an impact absorbing sleeve having void spaces in the wall thereof amounting to from about 30 to about 60 percent of the wall volume and having internal threads extending partially through the sleeve so as to terminate at a resulting shoulder of unthreaded cylinder wall; a metal shell having an internal methylpropylcyclohexanes, and the ethylpropylcyclohexanes.

Polyethylene made according to the'described method is light in weight and tough and has suincie'nt pliability coupled with high impact strength to withstand rugged service over a wide temperature range.

Tests in the laboratory and in rail, barge and truck shipments have shown that thread protectors made from the polyethylene described above had the necessary toughness and impact resistance to be satisfactory over the expected working temperature range of 50 F. and 150 F. :under the expected handling conditions. These tests showed that the polyethylene protectors cushioned the impact blows by dissipating the energy into deformation of the polyethylene cylindrical sleeve surrounding the threads. While the polyethylene has the ability to absorb the energy of impact blows th e material is subject to cutting and abrasion and the inevitable shifting of pipe in a load of pipe will result in damage to the polyethylene pro teetor and subsequently damage the threads if the abrasive action continues. The thread protectors of my 'invention combine the abrasion resistance of the metal cover with the impact absorption characteristic of the polyethylene sleeve so as to provide complete protection of the threaded article. 7 i 7 :Rigid polyethylene is deformable and pliable but is substantially incompressible and therefore sorhe void space must be provided in the polyethylene sleeve so as to provide impact absorption characteristics in the polyethylene sleeve. FIGURES 1, 2 and 3 show three'methods pluralityof longitudinal perforations, FIGURE 2 show .for providing this void space; FIGURE 1' showing a a diameter suflicient for a friction fit over-said sleeve, enclosing said sleeve with one open end flush with the threaded end of said sleeve and the other open end turned inwardly about the unthreaded end of said sleeve.

2. The protector of claim 1 wherein the sleeve has a plurality of longitudinal passageways therethrough.

3. The protector of claim 1 wherein the sleeve has a plurality of radial passageways therethrough.

4. The protector 'of claim 1 wherein the exterior of the sleeve comprises a plurality of longitudinal ridges.

5. The protector of claim 1 wherein the sleeve is rigid polyethylene. I

6. A thread protector comprising an impact-absorbing means having void spaces'therein amounting to about 30 to about percent by volume and having internal threads extending'at least partially through said impactabsorbing means; a metal shell surrounding said impactabsorbing means, said metal shell having one open end flush with the threaded end of said impact-absorbing means and the other open end turned inwardly overthe other end of saidimpactabsorbing means.

7. The protector of claim 6 wherein said impact-absorbing means comprises a metal sleeve having internal threads, said metal sleeve being substantially concentric withsaid shell and spaced therefrom forming anpannulus, and an impact-absorbing material positioned in the annulus between said metal sleeve and said shell.

Gray Ian. .1, 1907 839,834 2,061,151 Gunderman Nov. 17, 1936 2,251,897 Severn Aug. 5, 1941 2,617,751 Bickett Nov. 11, 1952 2,620,938 Iesnig Dec. 9, 1952 2,689,665 Martin Sept. 21, 1954 2,729,245 Northrop Jan. 3, 1956 2,761,493 Lenz -1 Sept. 4, 1956 Bulleri et a1 Aug. 26, 1958 

